EarthquakesAnd their impact on the lithosphere

Earthquakes

What is an Earthquake

General Information

Over 30,000 happen each year worldwide that are strong enough to be felt

Only about 75 major earthquakes take place each year many in remote regions

Powerful Earthquake Reported in Costa Rica - YouTube

What is an Earthquake

A vibration of the Earth produced by the rapid release of energy

Caused by slippage along a break in Earth’s crust

Focus and Epicenter

Focus – point within earth where the earthquake starts› Waves are produced here

Epicenter – location on the surface of Earth directly above the focus

Faults

Faults – fractures in earth’s crust and mantle where movement has occurred

Cause of Quakes

Elastic rebound hypothesis – explanation for the release of energy stored in deformed rocks

Earthquakes - Shock Waves Explained - YouTube

Elastic Rebound Hypothesis

Rocks are in the original position

Stress builds up due to tectonic forces› Builds energy

Energy is released › Earthquake

Land rebounds into new position

How Earthquakes Work - YouTube

Aftershocks

Aftershocks – movements that follow a major earthquake› Sometimes

destroy structures weakened by the quake

Foreshocks

foreshocks - Small earthquakes happening before the major quake› Can be felt days or even years before

Earthquakes

Measuring Earthquakes

Seismographs

Instruments that record earthquake waves

Earthquake waves

2 types› Surface waves› Body waves

seismic waves - YouTube

Surface waves

Travel along earths outer layer

Up and down as well as side to side motion

Especially damaging to buildings

Slower than body waves

Body waves

Pass through earth’s interior

P waves – push – pull or compression waves› Faster than S waves

S waves – shake particles at right angles› Cannot pass through

gases or liquids

S and P waves - YouTube

Locating earthquakes

Seismographs can be used to see the difference in velocity between p and s waves

Interval between 1st p wave arrival and 1st s wave arrival › Longer the interval the further

the distance from the earthquake

Uses 3 or more seismographs

Earthquake zones

Measuring earthquakes

2 types of measurement› Intensity

Amount of shaking based on damage

qualitative› Magnitude

Calculations of energy released using seismographs

Quantitative

Richter scale

Based on amplitude of largest seismic wave

Logarithmic› 10 fold increase in

wave amplitude of 1 on the magnitude scale 5.0 is 10X greater

than 4.0 Familiar but

outdated

Moment magnitude

Based on amount of displacement at a fault zone

More precise Many different factors

› Av. amount of movement› Area of surface break› Strength of broken rock

Most widely used because it measures amount of energy released

Earthquakes

Destruction from earthquakes

Damage to buildings

Depends on several factors› Intensity and duration› Nature of the material on which the

structure is built› Design of the structure

Liquefaction

Where loosely consolidated sediments are saturated with water, stable soil can turn to a liquid during earthquakes

Buildings may settle and collapse

Underground storage tanks and sewage lines may float to the surface

liquefaction

Tsunamis

Destructive waves› Aka tidal waves

Not actually anything to do with tides Slab of ocean floor is displaced vertically

along a fault Or when a quake sets off an underwater

landslide

Japan Tsunami first wave ground footage - YouTube

Other Dangers

Landslides – do the greatest damage› Soil and / or rock slopes fail

Fire – gas and electrical lines may be cut › when water lines are also cut, fires cannot

be stopped – San Francisco 1906

Resources http://

www.bing.com/images/search?q=earthquakes&view=detail&id=EE1FD8ED426AAF3B77312E9A9484D8B0658EAC20&first=1

http://www.bing.com/images/search?q=earthquakes&view=detail&id=0728B2E8AF7D936E47C7BF9A02B44B97B405CF78&first=1

http://www.bing.com/images/search?q=earthquakes+fault&view=detail&id=FA2489321AD8DF470812AF17BE0995E91DC3A1C6

http://www.bing.com/images/search?q=earthquakes+fault&view=detail&id=40D683DDF14E595D6D4E9C9CF4E6F0AF6CD34876

http://www.bing.com/images/search?q=focus+and+epicenter&view=detail&id=FB2A1080B026570F0D431369A72135CFDE80F499

http://www.bing.com/images/search?q=focus+and+epicenter&view=detail&id=5946B7F86F88FEDF8AEAAF8D365662ADEA32DC7B

http://www.bing.com/images/search?q=faults+in+layers+of+earth&view=detail&id=36DC8F18B91F95FB51F5D6AE26A6B8989CFA9262

http://geology1a-1.wikispaces.com/file/view/af1-2.jpg/91060621/af1-2.jpg

http://www.bing.com/images/search?q=elastic+rebound+hypothesis&view=detail&id=324E2B8DBD877E7D1F275E3EA579513E54AD1B37

http://www.bing.com/images/search?q=elastic+rebound+hypothesis&view=detail&id=7062BC2EA8C716E24F9C497D66852D25DBBCCF7C

http://www.bing.com/images/search?q=aftershocks&view=detail&id=8853BBAD1093CE083BA03EACCF30069118E4964F

http://www.bing.com/images/search?q=foreshocks&view=detail&id=D1940E7C9DDB185FE9A0627D885B1E22587545B8

http://www.bing.com/images/search?q=chinese+seismograhs&view=detail&id=E40AAF20E3AAFDF2518CF57BF82D246432021C20

http://www.bing.com/images/search?q=chinese+seismograhs&view=detail&id=83C14F9337C971D280DD7DBB312D5330507EE293

http://www.bing.com/images/search?q=seismographs&view=detail&id=CBCC79FBD4D64BC13E8303C4A3ECA227DCA919A3

http://www.bing.com/images/search?q=waves+of+earthquakes&view=detail&id=AEC862B742E9419C10F2E533EEBE78AABEA7FDC9

http://www.bing.com/images/search?q=waves+of+earthquakes&view=detail&id=33B413C8FEF8F53B2FAFAB1313C2C8A33A1801D2

http://www.sciencephoto.com/image/167086/530wm/E3600021-P_and_S_seismic_body_waves,_artwork-SPL.jpg

http://www.bing.com/images/search?q=s+waves+and+p+waves&view=detail&id=D48D39E039FEEE7140C63325836489C38C9C614F

http://www.bing.com/images/search?q=locating+quakes&view=detail&id=03AD9F4CEADBC08D30ECFFBA469757A1B281DBB1

More resources http://

www.bing.com/images/search?q=earthquake+zones&view=detail&id=A3F9FB5A69E1D039843C525F1BAF88159C66E083

http://www.bing.com/images/search?q=measuring+earthquakes&view=detail&id=B0094EED325431622BDF19EFA2AFAD11E44F9666

http://www.bing.com/images/search?q=richter+scale&view=detail&id=68579F29E8CD762823EC891EB5C8794EC51EA709

http://www.bing.com/images/search?q=moment+magnitude&view=detail&id=4D878897FBCA6B4E3805C8047D0365FAFAC739BB

http://www.bing.com/images/search?q=earthquake+damage+to+buidlings&view=detail&id=F5E5C8B45E5F45F6F091631C2EC236065EEFC0CD

http://www.bing.com/images/search?q=charleston+earthquake+bolts&view=detail&id=4C0D502CDE305E8C0BEE8908E67832D33E95ABC7

http://www.bing.com/images/search?q=liquefaction&view=detail&id=4EC6832420397B19256452B646F02EB09D096D33

http://www.bing.com/images/search?q=liquefaction&view=detail&id=328A257C25776AD3AF663F9412F83BF7E34EC497

http://www.bing.com/images/search?q=tsunami&view=detail&id=C188859273F9A8265A46DCF056BE058E9568162C

http://www.bing.com/images/search?q=tsunami&view=detail&id=9038EBFBAC6EE01E540C37E623206AE422AB9A39&first=119

http://www.bing.com/images/search?q=earthquake+landslides&view=detail&id=1B54A1285A4A2D03E769A8F49A2E86E26F1E4F84

http://www.bing.com/images/search?q=earthquake+fires&view=detail&id=979D85852B95F1347D623BFE9D2728FDAF28FD42